JP2000205025A - Control apparatus for engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain occurrence of uncomfortable low frequency vibrations to stabilize idling, decrease harmful exhaust emission and improve fuel economy, by stabilizing a combustion state of each cylinder during idling, and equalizing output torque between cylinders. SOLUTION: When it is determined that an engine is idling (S51, S52), a differential revolution mean value TCLAVE for each cylinder is calculated, and a differential revolution fluctuation amount integrated value TCLSUM is calculated by integrating an absolute value of difference between a differential revolution TCYLAC and the differential revolution fluctuation amount TCLAVE (S59, S66,...). An ignition timing correction amount is set based on the differential revolution mean value TCLAVE, and a fuel injection correction amount is set based on the differential revolution fluctuation amount integrated value TCLSUM. Then, a fuel injection amount and ignition timing of each of the cylinders is corrected to uniform a combustion state of each of the cylinder and variations in output torque for the cylinders. Thereby, occurrence of uncomfortable low frequency vibrations is restrained, harmful exhaust emission is decreased and fuel economy is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an engine control device for stabilizing the combustion state of each cylinder during idling operation and for equalizing the output torque between the cylinders.

[0002]

2. Description of the Related Art Generally, in order to improve the idling stability of an engine, it is necessary to suppress variations in the combustion state between cylinders. The combustion state of each cylinder has a strong correlation between the in-cylinder pressure (combustion pressure) of the cylinder during the combustion stroke and the engine rotation between the combustion stroke and the next combustion stroke. It is possible to make a determination based on a change in the engine rotation state quantity for each.

[0003] For example, Japanese Patent No. 2505304 discloses that when the engine is in an idle state, a difference in engine rotation for each predetermined crank angle is detected, and when the difference in engine rotation for a predetermined cylinder exceeds an upper limit value. The fuel injection correction amount of the cylinder is reduced by a set amount, and the fuel injection correction amounts of the other cylinders are equally distributed and increased in accordance with the reduced amount,
On the other hand, when the engine rotation fluctuation difference of the predetermined cylinder is lower than the lower limit value, the fuel injection correction amount of the cylinder is increased by a set amount, and the fuel injection correction amounts of the other cylinders are equally distributed and reduced in accordance with the increase amount. When the injection correction amount exceeds the allowable upper limit value or becomes lower than the allowable lower limit value, the ignition timing is advanced or retarded. Techniques are disclosed.

[0004]

However, in the above prior art, the correction of the fuel injection amount for each cylinder is mainly performed, and the ignition timing is set only when the injection correction amount of a predetermined cylinder reaches the upper limit value or the lower limit value. Therefore, since the correction is performed in a serial manner, it is inevitable that the fuel injection amount varies from cylinder to cylinder. As a result, it is not necessarily advantageous in reducing harmful exhaust emissions as a whole.

[0005] Further, when the engine rotation fluctuation difference becomes large due to a large intake air amount of a certain cylinder, the cylinder is burned with a low air-fuel ratio in order to reduce the fuel injection amount of the cylinder. , And the output torque decreases relative to the other cylinders. For this reason, there is a possibility that a swell-like rotation fluctuation occurs at a relatively long cycle, and the occupant may be uncomfortable.

The present invention has been made in view of the above circumstances, and suppresses the generation of unpleasant low-frequency vibrations by stabilizing the combustion state of each cylinder during idling and making the output torque between the cylinders uniform. It is an object of the present invention to provide an engine control device capable of stabilizing idle operation, reducing harmful exhaust emissions and improving fuel efficiency.

[0007]

In order to achieve the above object, the invention according to claim 1 comprises an engine rotational state quantity detecting means for detecting an engine rotational state quantity at every predetermined crank angle between cylinders, Cylinder discriminating means for discriminating the stroke cylinder, idle discriminating means for discriminating the idling state of the engine from the engine operating state, and, when the engine is idling, one combustion stroke from the engine rotation state quantity corresponding to the current combustion stroke cylinder. A differential rotation state amount calculating means for subtracting the engine rotation state amount corresponding to the previous cylinder and calculating the difference rotation state amount for the current combustion stroke cylinder, and averaging the differential rotation state amount for each cylinder in a predetermined period. And a differential rotation state amount average value calculating means for calculating as a differential rotation state amount average value for each cylinder; and the differential rotation state amount for each cylinder in a predetermined period. A differential rotation variation integrated value calculating means for integrating an absolute value of a difference from the differential rotation state average value and calculating as a differential rotation variation integrated value for each cylinder; A fuel injection control means for reducing the fuel injection amount for the cylinder having the smallest integrated value and increasing and correcting the fuel injection amount for the cylinder having the largest difference rotation variation amount integrated value; Ignition timing control means for advancing the ignition timing for the cylinder with the lowest value, and retarding the ignition timing for the cylinder with the highest differential rotation state quantity average value. I do.

According to a second aspect of the present invention, there is provided an engine rotational state amount detecting means for detecting an engine rotational state amount for each predetermined crank angle between cylinders, a cylinder determining means for determining a current combustion stroke cylinder, and an engine idle state. An idle determining means for determining a state from an engine operating state; and, when the engine is in an idle state, subtracting an engine rotational state quantity corresponding to a current combustion stroke cylinder from an engine rotational state quantity corresponding to a cylinder one combustion stroke earlier. A difference rotation state amount calculation means for calculating the difference rotation state amount for the current combustion stroke cylinder, and averaging the difference rotation state amount for each cylinder in a predetermined period, and calculating the difference rotation state amount average value for each cylinder. Means for calculating the average value of the differential rotation state amount, and integrating the absolute value of the difference between the differential rotation state amount and the average differential rotation state amount for each cylinder during a predetermined period. In other words, the differential rotation fluctuation amount integrated value calculation means for calculating the difference rotation fluctuation amount integrated value for each cylinder, and the fuel injection amount for the cylinder having the smallest difference rotation fluctuation amount integrated value during the idle state is corrected. And a fuel injection control means for increasing and correcting the fuel injection amount for the cylinder having the largest differential rotation fluctuation amount integrated value, and advancing the ignition timing for the cylinder having the highest differential rotation state amount average value. In addition, there is provided an ignition timing control means for retarding the ignition timing of the cylinder having the lowest differential rotation state amount average value.

According to a third aspect of the present invention, in the first or second aspect, the fuel injection control means includes:
In the idling state, a fuel injection correction amount for increasing or decreasing the fuel injection amount is set for each cylinder in accordance with the differential rotation fluctuation amount integrated value, and the fuel injection amount calculated based on the engine operating state is set for each cylinder. The fuel injection correction amount is corrected by the fuel injection correction amount to set the final fuel injection amount for each cylinder, and the cylinder-by-cylinder fuel injection correction amount is stored and held as a learning value and updated as needed. Setting an ignition timing correction amount for advancing or retarding the ignition timing according to the average value of the differential rotation state amount for each cylinder,
The ignition timing calculated based on the engine operating state is corrected by the above-described cylinder-specific ignition timing correction amount to set the final ignition timing for each cylinder, and the above-described cylinder-specific ignition timing correction amount is stored and held as a learning value, as needed. It is characterized by updating.

That is, according to the first aspect of the present invention, the amount of engine rotation for each predetermined crank angle between cylinders is detected, and when the engine is idling, one combustion stroke is calculated from the amount of engine rotation corresponding to the current combustion stroke cylinder. The engine rotation state amount corresponding to the previous cylinder is subtracted to calculate the difference rotation state amount for the current combustion stroke cylinder. Then, the average value of the differential rotation state amount for each cylinder is calculated by averaging the differential rotation state amount for each cylinder in the predetermined period, and the differential rotation state amount and the differential rotation state amount average value for each cylinder in the predetermined period. Is integrated to calculate an integrated value of the differential rotation fluctuation amount for each cylinder. Then, the fuel injection amount of the cylinder having the smallest differential rotation fluctuation amount is reduced and corrected, and the fuel injection amount is corrected to be increased for the cylinder having the maximum difference rotation fluctuation amount, so that the combustion state of each cylinder is corrected. In addition, by making the ignition timing of the cylinder with the lowest average value of the differential rotation state amount advance, and retarding the ignition timing of the cylinder with the highest average of the differential rotation state amount, the output torque between the cylinders is reduced. Suppress variations.

Further, as in the second aspect of the present invention, when the engine is in the idling state, the difference between the engine rotation state amount corresponding to the cylinder one combustion stroke before and the current combustion stroke is determined as the differential rotation state amount for the current combustion stroke cylinder. The calculation may be performed by subtracting the engine rotation state quantity corresponding to the cylinder.In this case, the ignition timing advance and retard corrections are reversed, and the ignition timing is calculated for the cylinder having the highest differential rotation state quantity average value. Is advanced, and the ignition timing is retarded for the cylinder having the lowest differential rotation state amount average value.

Further, according to the present invention, when correcting the fuel injection amount and the ignition timing in the idle state, the fuel injection for increasing or decreasing the fuel injection amount in accordance with the integrated value of the differential rotation fluctuation amount. The correction amount is set for each cylinder, and the final fuel injection amount is set for each cylinder by correcting the fuel injection amount calculated based on the engine operating state with the cylinder-specific fuel injection correction amount. Further, during the idle state, the ignition timing correction amount for advancing or retarding the ignition timing according to the average value of the differential rotation state amount is set for each cylinder, and the ignition timing calculated based on the engine operation state is set for each cylinder. The final ignition timing is set for each cylinder by correcting with the timing correction amount. The controllability is improved by storing and updating the learned fuel injection correction amount for each cylinder and the ignition timing correction amount for each cylinder as learning values as needed.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIGS. 1 to 14 relate to an embodiment of the present invention, FIGS. 1 to 4 are flowcharts of an idling stabilization control routine, FIG. 5 is a flowchart of a cylinder discrimination / engine speed calculation routine, and FIG. FIG. 7 is a flowchart of an injection control routine, FIG. 7 is a flowchart of a cylinder-specific ignition timing control routine, and FIG. 8 is a crank pulse, a cylinder discrimination pulse, a combustion stroke cylinder, an ignition timing,
And a time chart showing the relationship between fuel injection timing,
FIG. 9 is a timing chart showing the calculation state of the differential rotation for each cylinder, FIG. 10 is an explanatory diagram showing the fluctuation state of the differential rotation, and FIG.
1 is an overall schematic view of an engine, FIG. 12 is a front view of a crank rotor and a crank angle sensor, FIG. 13 is a front view of a cam rotor and a cylinder discrimination sensor, and FIG. 14 is a circuit configuration diagram of an electronic control system.

First, the overall structure of the engine will be described with reference to FIG. In the figure, reference numeral 1 denotes an engine, which in this embodiment is a horizontally opposed four-cylinder gasoline engine. Cylinder block 1a of this engine 1
In each of the left and right banks, a cylinder head 2 is provided, and an intake port 2a and an exhaust port 2b are formed in each cylinder head 2.

The intake system of the engine 1 includes an intake port 2a
An intake manifold 3 is communicated with the intake manifold 3, and a throttle chamber 5 is communicated with the intake manifold 3 via an air chamber 4 in which intake passages of the respective cylinders are gathered.
An intake pipe 6 is provided upstream of the throttle chamber 5.
The air cleaner 7 is attached via the air cleaner 7, and the air cleaner 7 is communicated with the air intake chamber 8.

The throttle chamber 5 is provided with a throttle valve 5a linked to an accelerator pedal. A bypass passage 9 that bypasses the throttle valve 5a is connected to the intake pipe 6, and the idle rotation speed is adjusted by adjusting the amount of bypass air flowing through the bypass passage 9 according to the valve opening during idling. An idle speed control valve (ISC valve) 10 to be controlled is interposed.

Further, an injector 11 is disposed immediately upstream of the intake port 2a of each cylinder of the intake manifold 3. The injector 11 is connected to a fuel tank 13 via a fuel supply path 12.
Is provided with an in-tank type fuel pump 14.
The fuel from the fuel pump 14 is pressure-fed to the injector 11 and the pressure regulator 16 via the fuel filter 15 interposed in the fuel supply path 12, returned from the pressure regulator 16 to the fuel tank 13, and sent to the injector 11. The fuel pressure is adjusted to a predetermined pressure.

On the other hand, an ignition plug 17 for exposing the discharge electrode at the tip to the combustion chamber is attached to each cylinder of the cylinder head 2, and an ignition coil 18 containing an igniter 19 is connected to the ignition plug 17. .

In the exhaust system of the engine 1, an exhaust pipe 21 is communicated with a collection portion of an exhaust manifold 20 which communicates with each exhaust port 2b of the cylinder head 2, and a catalytic converter 22 is interposed in the exhaust pipe 21. To the muffler 23.

Next, sensors for detecting the operating state of the engine will be described. Air cleaner 7 for intake pipe 6
A thermal intake air amount sensor 24 using a hot wire or a hot film or the like is interposed immediately downstream of the throttle valve 5.
A throttle opening sensor 25 for detecting the opening of the throttle valve 5a is provided in series.

The cylinder block 1a of the engine 1
A knock sensor 26 is mounted on the cooling water passage 2 which communicates the left and right banks of the cylinder block 1a.
7, a cooling water temperature sensor 28 is provided, and an O2 sensor 29 is disposed upstream of the catalytic converter 22 as an example of an air-fuel ratio sensor.

The crankshaft 30 of the engine 1
A crank angle sensor 32 is provided on the outer periphery of a crank rotor 31 which is axially mounted on the cam rotor 33. Further, a cam rotor 34 connected to a cam shaft 33 which makes a half rotation with respect to the crank shaft 30 has a current combustion stroke cylinder, A cylinder discriminating sensor 35 for discriminating a fuel injection target cylinder and an ignition target cylinder is provided in opposition.

As shown in FIG. 12, the crank rotor 31 has projections 31a, 31b, 31c formed on its outer periphery, and these projections 31a, 31b, 31c are connected to the cylinders (# 1, # 2 and # 2, respectively). 3, # 4 cylinder) before compression top dead center (BTDC) θ1, θ2, θ3. In the present embodiment, θ1 = 97 ° CA, θ2
= 65 ° CA, θ3 = 10 ° CA.

Also, as shown in FIG.
4 are provided on the outer periphery of the projections 34a, 34b, 34 for cylinder discrimination.
c, the projection 34a is formed at a position θ4 after the top dead center (ATDC) of compression of the # 3 and # 4 cylinders, and the projection 34b is composed of three projections, and the first projection is the ATD of the # 1 cylinder.
It is formed at the position of Cθ5. Further, when the protrusion 34c is 2
ATDC of # 2 cylinder
It is formed at the position of θ6. In the present embodiment, θ4 = 20 ° CA, θ5 = 5 ° CA, θ6 = 20 °
CA.

Then, as shown in the time chart of FIG. 8, the crank rotor 31 and the cam rotor 34 are rotated by the rotation of the crankshaft 30 and the camshaft 33 in association with the operation of the engine. 32, θ1, θ2, θ3 (BTDC 97 °, 65
, 10 °) is output every 1/2 engine revolution (180 ° CA). On the other hand, each projection of the cam rotor 34 is detected by the cylinder discrimination sensor 35 between the θ3 crank pulse and the θ1 crank pulse, and a predetermined number of cylinder discrimination pulses are output from the cylinder discrimination sensor 35.

An electronic control unit 40 (FIG. 1)
4), the engine rotation speed (engine speed) NE is calculated based on the input interval time Tθ of the crank pulse output from the crank angle sensor 32, and the combustion stroke order of each cylinder (for example, # 1 cylinder) → # 3 cylinder → # 2
The current combustion stroke cylinder, the fuel injection target cylinder, and the ignition target cylinder are determined based on a pattern of (cylinder → # 4 cylinder) and a value obtained by counting a cylinder determination pulse from the cylinder determination sensor 35 by a counter.

Injector 11, spark plug 17, IS
Calculation of control amounts for actuators such as the C valve 10;
Output of control signals, that is, engine control such as fuel injection control, ignition timing control, idle speed control, and the like is performed by an electronic control unit (ECU) 40 shown in FIG.

The ECU 40 includes a CPU 41, a ROM 42,
A RAM 43, a backup RAM 44, a counter / timer group 45, and an I / O interface 46 are mainly configured by a microcomputer connected to each other via a bus line, and a constant voltage circuit 47 for supplying a stabilized power to each unit. A peripheral circuit such as a drive circuit 48 and an A / D converter 49 connected to the O interface 46 is built in.

The counter / timer group 45 is used to generate various counters such as a free-run counter, a counter for counting the input of a cylinder discrimination sensor signal (cylinder discrimination pulse), a fuel injection timer, an ignition timer, and a periodic interrupt. Timers such as a timer for periodic interruption, a timer for measuring an input interval of a crank angle sensor signal (crank pulse), and a watchdog timer for monitoring a system abnormality are collectively referred to for convenience. A timer is used.

The constant voltage circuit 47 is connected to the battery 51 via a first relay contact of a power supply relay 50 having two relay contacts, and is also directly connected to the battery 51. When the switch is turned on and the contact of the power supply relay 50 is closed, power is supplied to each unit in the ECU 40, while the ignition switch 52 is turned on.
Regardless of ON or OFF, always backup RAM4
4 is supplied with power for backup. Further, the fuel pump 14 is connected to the battery 51 via a relay contact of the fuel pump relay 53. The power relay 50
A power line for supplying power from the battery 51 to each actuator is connected to the second relay contact.

The input port of the I / O interface 46 includes an ignition switch 52, a knock sensor 2
6, a crank angle sensor 32, a cylinder discriminating sensor 35, a vehicle speed sensor 36 for detecting a vehicle speed, and the like are connected. Further, via an A / D converter 49, the intake air amount sensor 24, the throttle opening The temperature sensor 25, the cooling water temperature sensor 28, the O2 sensor 29, and the like are connected, and the battery voltage VB is input and monitored.

On the other hand, the output port of the I / O interface 46 has a relay coil of the fuel pump
The SC valve 10, the injector 11, etc.
And the igniter 19 is connected.

The CPU 41 processes the detection signals from the sensors and switches, which are input via the I / O interface 46, the battery voltage, and the like, according to the control program stored in the ROM 42. Based on the data, various learning value data stored in the backup RAM 44, fixed data stored in the ROM 42, etc., the fuel injection amount for each cylinder, the ignition timing for each cylinder, the duty ratio of the drive signal for the ISC valve 10, etc. And engine control such as cylinder-specific fuel injection control, cylinder-specific ignition timing control, idle speed control, and the like.

In such an engine control system, EC
In U40, the crank angle sensor 32, the cylinder discrimination sensor 3
5, the current combustion stroke cylinder is determined based on the crank pulse and the cylinder determination pulse output from the respective cylinders. Also,
As an engine rotation state quantity for each predetermined crank angle between cylinders, a section that is hardly affected by combustion between the cylinders (a section in which no work is performed by combustion between a combustion stroke cylinder and the next combustion stroke cylinder). Detects engine speed. In the present embodiment, between BTDC θ2 and θ3, that is, θ
The engine rotation speed between the input of the 2, θ3 crank pulse is detected.

Then, the difference between the rotational speeds of the combustion stroke cylinders, that is, the combustion stroke cylinders, is subtracted from the engine rotational speed corresponding to the current combustion stroke cylinder, by subtracting the engine rotational speed corresponding to the cylinder one combustion stroke earlier in the same section from the previous time. And the two parameters obtained by processing the differential rotation TCYLAC for each cylinder to determine the ignition timing for each cylinder and the fuel injection amount for each cylinder during idling operation. to correct.

That is, in a multi-cylinder engine, if the combustion of a certain cylinder is unstable, not only unpleasant vibration is given to the occupant, but also harmful increase of exhaust emission and deterioration of fuel efficiency are caused. Therefore, in order to improve the stability at the time of idling, it is necessary to improve the combustion stability of each cylinder. However, the output torque between the cylinders may not be uniform by simply improving the combustion stability. If the output torque between the cylinders is non-uniform, there is a possibility that undulating rotation fluctuations, that is, low-frequency vibrations, and uncomfortable feeling may remain.

For this reason, the differential rotation TCYLAC for each cylinder
A parameter representing combustion stability for each cylinder and a parameter representing variation in output torque between cylinders are calculated based on the two parameters, and the fuel injection amount and the ignition timing for each cylinder are optimized using these two parameters. By controlling, the combustion stability of each cylinder is improved, and the variation of the output torque between the cylinders is suppressed.

The parameter representing the combustion stability of each cylinder includes a differential rotation TCYLAC of each cylinder during a predetermined period.
Difference rotation average value (difference rotation state quantity average value) T
A differential rotation variation integrated value TCLSUM obtained by integrating the absolute value of the difference between CLAVE and the differential rotation TCYLAC of each cylinder is used. Compared to other cylinders, differential rotation fluctuation integrated value TCL
A cylinder with a small SUM has a relatively small variation in combustion pressure and a stable combustion compared to the other cylinders. Conversely, a cylinder with a large differential rotation fluctuation integrated value TCLSUM as compared with the other cylinders has a relatively small difference. The fluctuation of the combustion pressure is larger than other cylinders, and the combustion is unstable. Therefore, the differential rotation fluctuation integrated value TCL
By repeating the process of reducing the fuel injection amount for the cylinder with the SUM being the smallest and increasing and correcting the fuel injection amount for the cylinder with the largest differential rotation fluctuation integrated value TCLSUM, the combustion state of each cylinder is made uniform and stable. Improve the performance.

The parameter representing the variation in torque among the cylinders is a differential rotation average value TCLAV for each cylinder.
E is used. Here, in the present embodiment, the differential rotation TCYLACi based on which the differential rotation average value TCLAVE of the cylinder #i is calculated is the current combustion stroke cylinder #i.
The engine rotation speed TCYLi corresponding to cylinder # i-1 one combustion stroke before the engine rotation speed TCYLi corresponding to
Calculated by subtracting -1. Therefore, a cylinder having a lower differential rotation average value TCLAVE as compared with the other cylinders is a cylinder having a lower combustion pressure and a smaller average output torque than the other cylinders. Average rotational difference TCL
A cylinder with a high AVE has a higher combustion pressure than other cylinders and a higher average output torque. Accordingly, the ignition timing for the cylinder with the lowest differential rotation average value TCLAVE is corrected in the direction in which the output torque increases, that is, toward the advanced angle, and the ignition timing for the cylinder with the highest differential rotation average value TCLAVE is adjusted in the direction in which the output torque decreases. In other words, the output torque for each cylinder is made uniform by repeating the process for correcting the retard side.

That is, the ECU 40 includes the rotational state quantity detecting means, the cylinder determining means, the idling determining means,
Difference rotation state amount calculation means, difference rotation state amount average value calculation means,
It has the functions of the differential rotation variation integrated value calculation means, the fuel injection control means, and the ignition timing control means. Specifically, the functions of each means are realized by each routine shown in FIGS.

Hereinafter, the processing relating to the idling stabilization control of the present invention executed by the ECU 40 will be described with reference to FIGS.
This will be described with reference to the flowchart shown in FIG.

First, the ignition switch 52 is turned on.
Then, when the power is supplied to the ECU 40, the system is initialized, and each flag and each counter are initialized except for data such as various learning values stored in the backup RAM 44. Then, when the engine is started, a cylinder discrimination / engine rotation speed calculation routine shown in FIG. 5 is executed every time a crank pulse is input from the crank angle sensor 32.

In this cylinder discriminating / engine rotational speed calculating routine, when the crank rotor 31 rotates and the crank pulse is inputted from the crank angle sensor 32 in accordance with the engine operation, first, in step S1, the presently inputted crank is inputted. Whether the pulse corresponds to the crank angle of θ1, θ2, or θ3 is identified based on the input pattern of the cylinder discrimination pulse from the cylinder discrimination sensor 35, and step S2 is performed.
Then, the cylinders such as the current combustion stroke cylinder, the ignition target cylinder, and the fuel injection target cylinder are determined from the input pattern of the crank pulse and the cylinder determination pulse.

That is, as shown in the time chart of FIG. 8, for example, if there is a cylinder discrimination pulse input between the previous crank pulse input and the present crank pulse input, the current crank pulse is The crank pulse can be identified as a θ1 crank pulse, and the crank pulse input next time can be identified as a θ2 crank pulse.

When there is no cylinder discrimination pulse input between the previous and current crank pulse inputs and there is a cylinder discrimination pulse input between the last two previous and previous crank pulse inputs, the current crank pulse becomes the θ2 crank pulse. The crank pulse input next time can be identified as the θ3 crank pulse. Further, when there is no cylinder discrimination pulse input between the previous and current times, and between the last and last crank pulse inputs, the currently input crank pulse can be identified as the θ3 crank pulse, and the next input crank pulse can be identified. The pulse can be identified as a θ1 crank pulse.

Here, in the four-cycle four-cylinder engine 1 according to the present embodiment, the combustion stroke is # 1 → # 3 → # 2
As shown in the time chart of FIG. 8, the cylinder to be ignited reaches the compression top dead center with respect to the current (current) combustion stroke cylinder CYL when the cylinder discrimination pulse is output (CYL + 1). The cylinder, the fuel injection target cylinder at this time,
The next two cylinders are (CYL + 3).

Therefore, when three cylinder discriminating pulses are inputted (the .theta.5 cylinder discriminating pulse corresponding to the projection 34b) between the previous and current crank pulse inputs, the next top dead center is # 3 cylinder, and It can be determined that the combustion stroke cylinder is # 1 cylinder, the ignition target cylinder is # 3 cylinder, and the fuel injection target cylinder is # 4 cylinder, two cylinders after it. When two cylinder discrimination pulses are input between the previous and current crank pulse inputs (the θ6 cylinder discrimination pulse corresponding to the projection 34c), the next top dead center is # 4 cylinder, and the current combustion stroke cylinder is Can be determined as cylinder # 2, the cylinder to be ignited is cylinder # 4, and the cylinder to be injected with fuel is cylinder # 3.

When one cylinder discrimination pulse is input (the .theta.4 cylinder discrimination pulse corresponding to the protrusion 34a) between the previous and current crank pulse inputs, and the previous compression top dead center discrimination is for the # 4 cylinder. The next compression top dead center is # 1 cylinder, the current combustion stroke cylinder is # 4 cylinder, and the ignition target cylinder is #
One cylinder and the fuel injection cylinder can be determined to be # 2 cylinders. Similarly, when one cylinder discrimination pulse is input between the previous and current crank pulse inputs and the previous compression top dead center determination was # 3 cylinder, the next compression top dead center is # 2 cylinder, The current combustion stroke cylinder can be determined as # 3 cylinder, the ignition target cylinder is # 2 cylinder, and the fuel injection target cylinder is # 1 cylinder.

Thereafter, the process proceeds from step S2 to step S3, in which the time from the previous crank pulse input to the present crank pulse input measured by the crank pulse input interval timer is read, and the crank pulse input interval time Tθ (θ1 crank time) is read. Input interval time Tθ12 between pulse and θ2 crank pulse, θ2 crank pulse and θ3
Input interval time Tθ23 of crank pulse or input interval time Tθ of θ3 crank pulse and θ1 crank pulse
31) is detected.

Next, the routine proceeds to step S4, where the angle between the crank pulses corresponding to the crank pulse identified this time is read, and the current engine speed (engine speed) is determined based on the crank pulse angle and the crank pulse input interval time Tθ. ) NE is calculated, stored at a predetermined address in the RAM 43, and the routine exits. Note that the angle between crank pulses is known and is stored in advance as fixed data in the ROM 42. In the present embodiment, the angle between the θ1 crank pulse and the θ2 crank pulse is 32 ° CA, The angle between the crank pulse and the θ3 crank pulse is 55 ° CA, and the angle between the θ3 crank pulse and the θ1 crank pulse is 93 ° CA. In consideration of the engine start, the engine speed NE
Is calculated at, for example, 150 rpm or more.

The cylinder discrimination result of the present combustion stroke cylinder is executed each time a θ3 crank pulse is input.
In the idle stabilization control routine, the data of the combustion stroke cylinder CYL and the engine rotational speed NE are read out, and the differential rotation TC corresponding to the corresponding combustion stroke cylinder is read out.
YLAC is calculated, and based on the differential rotation TCYLAC, a differential rotation average value TCLAVE as a parameter representing a variation in output torque between cylinders, and a differential rotation variation integrated value TCLSUM as a parameter representing a combustion variation for each cylinder.
Is calculated.

In the idle stabilization control routine, first,
In step S51, the duty ratio of the drive signal for driving the ISC valve 10 is varied based on the difference between the engine speed and the target speed, and the opening of the ISC valve 10 is controlled to control the amount of air passing through the bypass passage 9. It is checked whether or not so-called ISC closed loop control is being performed to control the engine speed to converge to the target speed by increasing or decreasing the speed.

When it is determined that the ISC closed loop control is not being performed and the current operation state is not the idle operation state, the process branches from step S51 to step S53, and the calculation counters N1, N2 are counted up in each operation cycle. Initialize N3 and N4 to 0 and exit the routine. When the ISC closed loop control is being performed, the process proceeds from step S51 to step S52, where the absolute value | ΔN | of the fluctuation range (rotational deviation) of the engine speed at every predetermined time or every operation cycle is compared with a set value NS.
Even if the current operation state is under the ISC closed loop control, it is checked whether the current operation state is not a transient state such as a time of deceleration.

As a result, | ΔN |> NS and ISC
If the vehicle is in the transient state even during the closed loop control, the routine exits from the step S52 through the above-described step S53, and | ΔN | ≦ NS. If the engine is idling at step S52, the process proceeds from step S52 to step S54 and thereafter, and after calculating the differential rotation TCYLAC corresponding to the combustion stroke cylinder with a predetermined number of operation cycles,
Differential rotation average value TCLAV obtained by averaging differential rotation TCYLAC
E, a differential rotation variation integrated value TCLSU obtained by integrating the absolute value of the difference between the differential rotation TCYLAC and the differential rotation average value TCLAVE.
M is calculated, the ignition timing correction amount is set based on the differential rotation average value TCLAVE, and the differential rotation fluctuation integrated value TC
A process for setting a fuel injection correction amount based on the LSUM is performed.

That is, in step S54, the cylinder discrimination /
The current combustion stroke cylinder data CYL determined by the cylinder in the engine rotation speed calculation routine is read, and it is checked whether the current combustion stroke cylinder is # 1 cylinder. And CYL
= 1, that is, if the current combustion stroke cylinder is the # 1 cylinder, the routine proceeds to step S55, where the cylinder is calculated based on the input interval time Tθ23 between the θ2 crank pulse and the θ3 crank pulse by the cylinder determination / engine speed calculation routine. The engine speed NE between BTDC θ2 and θ3 is read, and the engine speed TCY corresponding to the combustion stroke cylinder # 1 in the current calculation cycle by the calculation counter N1.
L1 (N1) (TCYL1 (N1) ← NE).

Next, the routine proceeds to step S56, in which the engine rotation speed TCYL4 (N1) corresponding to the # 4 cylinder one combustion stroke earlier than the engine rotation speed TCYL1 (N1) corresponding to the combustion stroke cylinder # 1 in the current calculation cycle. Is subtracted to calculate the change in the engine rotation speed for each predetermined crank angle between the cylinders, that is, the differential rotation TCYLAC1 (N1) corresponding to the current combustion stroke cylinder # 1 cylinder (TCYLAC1 (N1) ← TCYL1 (N1) ) -TC
YL4 (N1)).

In the following step S57, the calculation counter N
1 is counted up (N1 ← N1 + 1), and step S is performed.
At 58, the calculation counter N1 sets the differential rotation TCYLAC1 (N
It is checked whether or not the number of cycles required to obtain the number of data required to calculate the average value of 1) has been reached. In the present embodiment,
In order to calculate the average value of the ten data of the differential rotation TCYLAC1 (N1), when N1 <10 in step S58, the routine exits and the differential rotation TCYLAC1 (N1) is exited.
Continue the data acquisition of 1), and when N1 = 10,
Proceed to step S59.

In step S59, the differential rotation TCYLAC
The value obtained by summing 1 (N1) for N1 = 1 to 10 is 10
To calculate the differential rotation average value TCLAVE1 of the # 1 cylinder (TCLAVE1 ← Σ (TCYLAC1 (N1)).
/ 10; N1 = 1 to 10), and differential rotation TCYLAC
1 (N1) and the absolute value of the difference between the differential rotation average value TCLAVE1 are integrated for N1 = 1 to 10 to calculate a differential rotation fluctuation integrated value TCLSUM1 (TCLSUM1 ← Σ (|
TCYLAC1 (N1) −TCLAVE1 |); N1 =
1 to 10).

Then, the process proceeds to a step S60, wherein # 1 indicates that the calculation of the 10th cycle for the # 1 cylinder has been completed.
When the cylinder 10 cycle end flag FCALC1 is set (FCALC1 ← 1), the process proceeds to step S82, where # 1 is set.
Flags FCALC1, FCALC2, and FCALC1 indicating that the calculation of 10 cycles for each cylinder of # 4 to # 4 has been completed.
See CALC3, FCALC4. When all the flags are set to 1 and the calculation of 10 cycles is completed in all the cylinders # 1 to # 4,
Proceeds to the processing of step S83 and thereafter, and sets the flag FCALC
If at least one of 1, FCALC2, FCALC3, and FCALC4 has a flag that is not set to 1, that is, if there is a cylinder for which the computation of 10 cycles has not been completed, the routine is exited and the computation is continued. .

In step S54, CYL #
If 1, the current combustion stroke cylinder is not the # 1 cylinder, the flow branches to step S61 to check whether CYL = 2, that is, whether the current combustion stroke cylinder is the # 2 cylinder. And C
If YL = 2 and the current combustion stroke cylinder is # 2 cylinder, the process proceeds to step S62, where BTDC θ2, θBT
The engine speed NE is read between three engine speeds NE, and the engine speed NE is set as the engine speed TCYL2 (N2) corresponding to the combustion stroke cylinder # 2 in the current calculation cycle by the calculation counter N2 (TCYL2 (N2) ← N
E).

Then, the process proceeds to a step S63, wherein the engine speed TCYL2 (N2) corresponding to the combustion stroke cylinder # 2
The engine rotation speed TCYL3 (N2) corresponding to the # 3 cylinder one combustion stroke before is subtracted from the engine rotation speed TCYL3 (N2), and the difference rotation TCYLAC2 (N) corresponding to the # 2 cylinder which is the current combustion stroke cylinder is subtracted.
2) is calculated (TCYLAC2 (N2) ← TCYL2
(N2) -TCYL3 (N2)).

In the following step S64, the calculation counter N
2 is counted up (N2 ← N2 + 1), and step S
At 65, it is checked whether or not the calculation counter N2 has reached 10. When N2 <10, the process exits the routine and continues data acquisition. When N2 = 10, the process proceeds to step S6.
6, the differential rotation TCYLAC2 (N2) is set to N2 = 1.
By dividing the sum of the values for to 10 by 10 to calculate the differential rotation average value TCLAVE2 of the # 2 cylinder (TCLAVE2
← Σ (TCYLAC2 (N2)) / 10; N2 = 1 to 1
0), and a differential rotation fluctuation integrated value TCLSUM2 obtained by integrating the absolute value of the difference between the differential rotation TCYLAC2 (N2) and the differential rotation average value TCLAVE2 for N2 = 1 to 10 is calculated (TCLSUM2 ← Σ (| TCYLAC2 ( N
2) -TCLAVE2 |)).

Next, the process proceeds to a step S67, in which # 2 indicates that the calculation of the 10th cycle for the # 2 cylinder is completed.
When the cylinder 10 cycle end flag FCALC2 is set (FCALC2 ← 1), in step S82, each flag FCALC1 to FCALC4 is referred to. If all the flags are set to 1, the process proceeds to step S83 and subsequent steps. If at least one flag is not set to 1, the routine is exited and the operation is continued.

In step S61, CYL ≠ 2
If the current combustion stroke cylinder is not the # 2 cylinder, the process branches from step S61 to step S68 to execute CY.
It is checked whether L = 3, that is, whether the current combustion cylinder is # 3 cylinder. If CLY = 3, steps S69 to S7
Similarly, the engine rotation speed TCYL1 (N3) corresponding to the # 1 cylinder one combustion stroke before is subtracted from the engine rotation speed TCYL3 (N3) corresponding to the # 3 cylinder via the engine rotation speed TCYL1 (N3) corresponding to the cylinder # 3. Differential rotation TCYLAC3 (N3)
Is calculated for 10 cycles of N3 = 1 to 10.

Next, the routine proceeds to step S73, where the differential rotation T
The value obtained by summing CYLAC3 (N3) for N3 = 1 to 10 is divided by 10 to obtain the differential rotation average value TCLA of the # 3 cylinder.
VE3 is calculated (TCLAVE3 ← Σ (TCYLAC3
(N3)) / 10; N3 = 1 to 10) and the differential rotation T
When a differential rotation fluctuation amount integrated value TCLSUM3 is calculated by integrating the absolute value of the difference between CYLAC3 (N3) and the differential rotation average value TCLAVE3 for N3 = 1 to 10, (TCLSU
M3 ← Σ (| TCYLAC3 (N3) -TCLAVE3
|)), In step S74, a # 3 cylinder 10-cycle end flag FCALC3 indicating that the calculation of 10 cycles for the # 3 cylinder has been completed is set (FCALC3 ←←).
1) The process proceeds to step S82.

Further, in step S68, CYL ≠ 3
If the current combustion stroke cylinder is not the # 3 cylinder, the process branches from step S68 to step S75, where CY
It is checked whether L = 4, that is, whether the current combustion cylinder is # 4 cylinder. If CYL ≠ 4, that is, if the cylinder discrimination has not been performed, the process jumps to step S53 to initialize the calculation counters N1 to N4 and exit from the routine. If CYL = 4, the process proceeds to steps S76 to S79. The engine rotation speed TCYL4 (N
The engine rotation speed TCYL2 (N4) corresponding to the # 2 cylinder one combustion stroke before is subtracted from 4), and the differential rotation TCYLAC4 (N4) corresponding to the # 4 cylinder is calculated for 10 cycles of N4 = 1 to 10.

Then, in step S80, the differential rotation TCY
The value obtained by summing LAC4 (N4) for N4 = 1 to 10 is divided by 10 to obtain a differential rotation average value TCLAVE of the # 4 cylinder.
4 (TCLAVE4 ← Σ (TCYLAC4 (N
4)) / 10; N4 = 1 to 10), and differential rotation TCY
A differential rotation fluctuation amount integrated value TCSUM4 is calculated by integrating the absolute value of the difference between LAC4 (N4) and the differential rotation average value TCLAVE4 for N4 = 1 to 10 (TCLSUM4 ←
Σ (| TCYLAC4 (N4) -TCLAVE4
|)). Then, in step S81, it is indicated that the calculation of ten cycles for the # 4 cylinder has been completed.
Set the cycle end flag FCALC4 (FCAL
C4 ← 1), and proceed to step S82.

As described above, the differential rotations TCYLAC1 to TCYLAC4 corresponding to each cylinder are calculated as shown in FIG.
10 of differential rotation TCYLAC1 to 4 for all four cylinders
The cycle calculation is completed, and the average values TCLAVE1 to TCLAVE4,
When the differential rotation fluctuation amount integrated values TCLSUM1 to TCLSUM4 have been calculated, in step S82, all the flags FCCALC1 to FCALCF
Since CALC4 is 1, the process proceeds to step S83 and subsequent steps.

In the processing after step S83, in steps S83 to S96, the differential rotation average value TCLAV for each cylinder is set.
For E1 to E4, the lowest cylinder and the highest cylinder are examined, and the ignition timing of each cylinder for advancing and retarding the ignition timing for the cylinder having the lowest differential rotation average value TCLAVE and the cylinder having the highest difference, respectively. The correction amount is corrected by decreasing or increasing the set value, and the ignition timing correction amount for each cylinder is updated as needed. Further, in steps S97 to S105, the minimum cylinder and the maximum cylinder are checked for the differential rotation fluctuation amount integrated values TCLSUM1 to TCLSUM1 to 4 for each cylinder, and the fuel injection amounts are respectively determined for the minimum cylinder and the maximum cylinder. The fuel injection correction amount for each cylinder for the decrease correction and the increase correction is corrected by decreasing or increasing the set value, and the fuel injection correction amount for each cylinder is updated as needed.

That is, for example, as shown in FIG.
When the fluctuation of the differential rotation TCYLAC1 of one cylinder is large, this fluctuation finally appears in a differential rotation fluctuation integrated value TCLSUM1 obtained by integrating the absolute value of the difference between the differential rotation TCYLAC1 and the differential rotation average value TCLAVE1. In such a case, #
It has been confirmed by simulations or experiments that fluctuations in differential rotation occur because the air-fuel ratio of one cylinder is thin. Therefore, in this case, the amount of fuel supplied to the # 1 cylinder is increased to enrich the air-fuel ratio. By correcting in the direction, the combustion state is improved and the stability is improved.

Further, as shown in FIG. 10, the average differential rotational speed TCLAVE2 of the # 2 cylinder is lower than the average differential rotational speed TCLAVE1 of the # 1 cylinder, and the average output torque of the # 2 cylinder is lower than the average output torque of the # 1 cylinder. When the average output torque is small, low-frequency vibration is generated in the vehicle body, which may cause discomfort to the occupant. Accordingly, in addition to increasing the amount of fuel supplied to the # 1 cylinder and improving combustion stability, the average output torque is increased by advancing the ignition timing of the # 2 cylinder, thereby making the output torque between the cylinders uniform. , Suppresses generation of unpleasant low frequency vibration.

Therefore, first, in step S83, #
The differential rotation average value TCLAVE1 of one cylinder is the lowest value M among the differential rotation average values TCLAVE1 to TCLAVE1 of cylinders # 1 to # 4.
It is checked whether it is IN (TCLAVE1, 2, 3, 4). Then, the differential rotation average value TCLAVE1 of the # 1 cylinder
Is the lowest, in step S84, the backup R
The ignition timing correction amount ADVKCL1 of the # 1 cylinder stored in the AM 44 as the learned value is updated by decreasing the set value A (ADVKCL1 ← ADVKCL1-A), and the process proceeds to step S90.

The ignition timing correction amount ADVKCL1 for the # 1 cylinder stored in the backup RAM 44 and the ignition timing correction amount ADVKCL for the # 2 to # 4 cylinders described below.
In the present embodiment, 2 to 4 are given as addition terms to the crank angle converted ignition timing θIG in the cylinder-specific ignition timing control routine of FIG. 7 described later, and the initial values are 0 corresponding to no correction. is there. The ignition timing correction amounts ADVKCL1 to ADVKCL4 may be given as multiplication terms. In this case, the initial value is 1.0 corresponding to no correction.
It is.

If it is determined in step S83 that the average rotational speed difference TCLAVE1 of the # 1 cylinder is not the lowest value, the process branches from step S83 to step S85, and proceeds to step # 85.
The cylinder difference rotation average TCLAVE2 is the lowest value MIN
(TCLAVE1, 2, 3, 4) is checked. If the differential rotation average value TCLAVE2 of the # 2 cylinder is the lowest, the backup RAM is determined in step S86.
The ignition timing correction amount ADVKCL2 of the # 2 cylinder stored in the learning value 44 is reduced by the set value A and updated (ADVKCL2 ← ADVKCL2-A), and the process proceeds to step S90.

On the other hand, if it is determined in step S85 that the differential rotation average value TCLAVE2 of the # 2 cylinder is not the lowest value, the flow branches from step S85 to step S87 to # 3.
The cylinder difference rotation average TCLAVE3 is the lowest value MIN
(TCLAVE1, 2, 3, 4) is checked. If the differential rotation average value TCLAVE3 of the # 3 cylinder is the lowest, the backup RAM is determined in step S88.
The ignition timing correction amount ADVKCL3 of the # 3 cylinder stored as a learning value in 44 is updated by decreasing the set value A (ADVKCL3 ← ADVKCL3-A), and the routine proceeds to step S90.

Further, if the average rotational speed difference TCLAVE3 of the # 3 cylinder is not the lowest value in step S87, the average rotational speed difference TCLAVE4 of the # 4 cylinder becomes the lowest value in this case, so that the process proceeds from step S87 to step S89. Then, the ignition timing correction amount ADVKCL4 of the # 4 cylinder stored as the learning value in the backup RAM 44 is reduced and updated by the set value A (ADVKCL4 ← ADVK).
CL4-A), and proceeds to step S90.

In step S90, the differential rotation average TCLAVE1 of the # 1 cylinder is changed to the differential rotation average T of the # 1 to # 4 cylinders.
The highest value MAX (TCLAV of CLAVE1 to 4)
E1, 2, 3, 4), and if the differential rotation average value TCLAVE1 of the # 1 cylinder is the highest, step S
At 91, the ignition timing correction amount ADVKCL1 of the # 1 cylinder stored as a learning value in the backup RAM 44 is updated by increasing the set value A (ADVKCL1 ← ADV).
KCL1 + A), and proceeds to step S97.

If it is determined in step S90 that the average rotational speed difference TCLAVE1 of the # 1 cylinder is not the highest value, the process branches from step S90 to step S92, and the average rotational speed difference TCLAVE2 of the # 2 cylinder is the highest value MAX (TCLA).
VE1, 2, 3, 4). And
When the differential rotation average value TCLAVE2 of the # 2 cylinder is the highest, the ignition timing correction amount AD of the # 2 cylinder stored as the learning value in the backup RAM 44 in step S93.
VKCL2 is increased by the set value A and updated (ADVK
CL2 ← ADVKCL2 + A), and proceeds to step S97.

On the other hand, if the average rotational speed difference TCLAVE2 of the # 2 cylinder is not the highest value in step S92, the process branches from step S92 to step S94, and the differential rotational speed average value TCLAVE3 of the # 3 cylinder is the highest value MAX (TCLA).
VE1, 2, 3, 4). And
If the differential rotation average value TCLAVE3 of the # 3 cylinder is the highest, the ignition timing correction amount AD of the # 3 cylinder stored as the learning value in the backup RAM 44 in step S95.
VKCL3 is increased by the set value A and updated (ADVK3
CL3 ← ADVKCL3 + A), and proceeds to step S97.

If it is determined in step S94 that the differential rotation average value TCLAVE3 of the # 3 cylinder is not the highest value, the process proceeds from step S94 to step S96 because the differential rotation average value TCLAVE4 of the # 4 cylinder is the highest value. Then, the ignition timing correction amount ADVKCL4 of the # 4 cylinder stored as a learning value in the backup RAM 44 is updated by increasing the set value A (ADVKCL4 ← ADVK).
CL4 + A), and proceeds to step S97.

After step S97, the cylinder-by-cylinder fuel injection correction amounts INJKCL1 to INJKCL1 to 4 stored in the backup RAM 44 are set and updated based on the differential rotation fluctuation amount integrated values TCLSUM1 to TCLSUM4 for each cylinder. In the present embodiment, the cylinder-specific fuel injection correction amount INJKCL1
4 is given as an addition term to the fuel injection pulse width Ti that determines the fuel injection amount in the cylinder-by-cylinder fuel injection control routine of FIG. 6 described later, and the initial value is 0 corresponding to no correction. The cylinder-specific fuel injection correction amount INJK
CL1 to CL4 may be given as a multiplication term (however, it is desirable to give them as a multiplication term with respect to an effective pulse width (Tp × α × COEF) when setting a fuel injection pulse width Ti described later). Is 1.0, which corresponds to the initial value without correction.

For this reason, first, in step S97, # 1
The cylinder difference rotation fluctuation integrated value TCLSUM1 is # 1 to # 4
It is checked whether or not it is the minimum value MIN (TCLSUM1, 2, 3, 4) of the cylinder difference rotation fluctuation integrated values TCLSUM1 to TCLSUM4. Then, the differential rotation variation integrated value T of the # 1 cylinder
When CLSUM1 is the minimum, the process proceeds to step S98, in which the fuel injection correction amount INJKCL1 of the # 1 cylinder stored as the learning value in the backup RAM 44 is updated by decreasing the set value B (INJKCL1 ← INJKC).
L1-B), and proceed to step S104.

If it is determined in step S97 that the differential rotation fluctuation integrated value TCLSUM1 of the # 1 cylinder is not the minimum, the process branches from step S97 to step S99, and the differential rotation fluctuation integrated value TCLSUM2 of the # 2 cylinder is reduced to the minimum value MIN. (T
CLSUM1, 2, 3, 4) is checked. When the differential rotation fluctuation integrated value TCLSUM2 of the # 2 cylinder is the minimum, the backup RA is determined in step S100.
The fuel injection correction amount INJKCL2 for the # 2 cylinder stored as the learning value in M44 is updated by decreasing the set value B (INJKCL2 ← INJKCL2-B), and the process proceeds to step S104.

On the other hand, if it is determined in step S99 that the differential rotation fluctuation integrated value TCLSUM2 of the # 2 cylinder is not the minimum, the process branches from step S99 to step S101, and the differential rotation fluctuation integrated value TCLSUM3 of the # 3 cylinder is reduced to the minimum value MIN.
(TCLSUM1, 2, 3, 4) is checked. Then, the differential rotation variation integrated value TCLSU of the # 3 cylinder is
If M3 is the minimum, the fuel injection correction amount INJKCL3 of the # 3 cylinder stored in the backup RAM 44 as the learning value is reduced by the set value B and updated in step S102 (INJKCL3 ← INJKCL3-B).
Proceed to step S104.

If it is determined in step S101 that the differential rotation fluctuation integrated value TCLSUM3 of the # 3 cylinder is not the minimum, the differential rotation fluctuation integrated value TCLSUM4 of the # 4 cylinder is not obtained.
Is minimized, so that steps S101 to S1
03, the fuel injection correction amount INJKCL for the # 4 cylinder stored in the backup RAM 44 as the learning value.
4 is reduced by the set value B and updated (INJKCL4 ←
INJKCL4-B), and proceeds to step S104.

In step S104, the differential rotation fluctuation integrated value TCLSUM1 of the # 1 cylinder is the maximum value MAX among the differential rotation fluctuation integrated values TCLSUM1-4 of the # 1 to # 4 cylinders.
(TCLSUM1, 2, 3, 4) is checked. Then, the differential rotation fluctuation integrated value TCLSU of the # 1 cylinder
If M1 is the maximum, the process proceeds to step S105, where the learning value is stored in the backup RAM 44 as #
The fuel injection correction amount INJKCL1 for one cylinder is updated by increasing the set value B (INJKCL1 ← INJKCL1 +
B), at step S111, calculation counters N1 to N4
Is cleared to 0, and the flags FCALC1-FCALC
Clear ALC4 to 0 and exit the routine.

If it is determined in step S104 that the integrated value of the differential rotation fluctuation amount TCLSUM1 of the # 1 cylinder is not the maximum,
Branching from step S104 to step S106, # 2
The cylinder difference rotation fluctuation integrated value TCLSUM2 is the maximum value MA.
It is checked whether X (TCLSUM1, 2, 3, 4). Then, the differential rotation fluctuation integrated value TCLSU of the # 2 cylinder
If M2 is the maximum, the fuel injection correction amount INJKCL2 of the # 2 cylinder stored as a learning value in the backup RAM 44 is updated by increasing the set value B by a set value B in step S107 (INJKCL2 ← INJKCL2 + B).
The process exits the routine via the above-described step S111.

On the other hand, if it is determined in step S106 that the differential rotation fluctuation amount integrated value TCLSUM2 of the # 2 cylinder is not the maximum,
The process branches from step S106 to step S108, and # 3
The cylinder difference rotation fluctuation integrated value TCLSUM3 is the maximum value MA.
It is checked whether X (TCLSUM1, 2, 3, 4). Then, the differential rotation variation integrated value TCLSU of the # 3 cylinder is
When M3 is the maximum, the fuel injection correction amount INJKCL3 of the # 3 cylinder stored as a learning value in the backup RAM 44 is updated by increasing the set value B in step S109 (INJKCL3 ← INJKCL3 + B).
The process exits the routine via step S111.

If it is determined in step S108 that the differential rotation fluctuation integrated value TCLSUM3 of the # 3 cylinder is not the maximum, the differential rotation fluctuation integrated value TCLSUM4 of the # 4 cylinder is not obtained.
Is the maximum, so that steps S108 to S1
Proceeding to 10, the fuel injection correction amount INJKCL for the # 4 cylinder stored as the learning value in the backup RAM 44
4 is increased by the set value B and updated (INJKCL4 ←
INJKCL4 + B), and exits the routine via step S111.

The cylinder-by-cylinder fuel injection correction amount INJKCLi (i = 1 to 4) which is updated as needed by the idle stabilization control routine and stored in the backup RAM 44.
4), cylinder-specific ignition timing correction amount ADVKCLi (i = 1 to
4) are read out by the cylinder-by-cylinder fuel injection control routine of FIG. 6 and the cylinder-by-cylinder ignition timing control routine of FIG. 7, respectively, and the fuel injection amount and the ignition timing during the idling operation are corrected.

In the fuel injection control routine shown in FIG. 6, in step S201, the engine operating state parameters are read from the output signals of the sensors, and in step S202, the fuel injection target cylinder determined in the cylinder determination / engine rotation speed calculation routine. For #i, the fuel injection pulse width Ti that determines the fuel injection amount is set. Fuel injection pulse width Ti
Is, as is well known, the intake air amount Q and the engine speed NE.
And the basic fuel injection pulse width Tp (= K × Q
/ NE; K is a constant), various increase correction coefficients COEF based on engine operating conditions such as cooling water temperature correction and acceleration / deceleration correction,
The air-fuel ratio is corrected by multiplying by an air-fuel ratio feedback correction coefficient α based on the output signal of the O2 sensor 29. Further, various increase correction coefficients COEF and air-fuel ratio feedback correction coefficient α
Is set by adding the voltage correction pulse width Ts for compensating for the invalid injection time of the injector 11 to the effective pulse width (Tp × α × COEF) by (Ti ← Tp × α × COEF)
+ Ts).

Next, the routine proceeds to step S203, where it is determined whether or not the current operation state is an idle state. This idling determination is performed by the same processing as in steps S51 and S52 of the above-described idling stabilization control routine. If the current operating state is not the idle state, step S206.
Then, a drive signal corresponding to the fuel injection pulse width Ti is output to the injector 11 of the fuel injection target cylinder #i at a predetermined timing, and the routine exits.

When the current operating state shifts to the idle state, the process proceeds from step S203 to step S204, in which the fuel injection correction amount INJK of the fuel injection target cylinder #i stored in the backup RAM 44 as a learning value.
CLi is read, and in step S205, the fuel injection correction amount INJKCLi is added to the fuel injection pulse width Ti.
The fuel injection pulse width Ti that determines the final fuel injection amount for each cylinder during idling is defined as (Ti ← Ti + INJKC
Li), in step S206, the fuel injection pulse width T
A drive signal corresponding to i is output to the injector 11 of the fuel injection target cylinder #i at a predetermined timing, and the routine exits.

That is, the differential rotation fluctuation amount integrated value TCLSU
By increasing the fuel injection amount for the cylinder with the smallest M, and decreasing the fuel injection amount for the cylinder with the largest differential rotation fluctuation amount TCLSUM, the cylinder with a relatively low air-fuel ratio and the air-fuel ratio This reduces the variation in the air-fuel ratio with the cylinders with darker cylinders and makes the combustion state of each cylinder uniform.

On the other hand, in the ignition timing control routine of FIG.
First, in step S301, the ignition target cylinder # determined in the cylinder determination / engine rotation speed calculation routine.
For i (= CYL + 1), the map is based on the engine load (in this embodiment, the basic fuel injection pulse width that determines the basic fuel injection amount determined by the intake air amount and the engine speed) Tp and the engine speed NE. The crank angle-converted basic ignition timing θBASE is set by reference or the like.

Next, the routine proceeds to step S302, where the knock control value θ is determined based on the output signal of knock sensor 26.
After setting NK, it is determined in step S303 whether or not the current operating state is an idle state. As a result, if the current operating state is not the idle state, step S3
03 to step S304, the basic ignition timing θBA
SE is corrected by knock control value θNK to set ignition timing θIG (θIG ← θBASE + θNK).

On the other hand, if the current operating state is the idle state, the process proceeds from step S303 to step S305, in which the ignition timing correction amount ADVKC of the ignition target cylinder #i stored in the backup RAM 44 as a learning value.
Li is read, and in step S306, the basic ignition timing θ
The ignition timing θIG is set by adding the knock control value θNK and the ignition timing correction amount ADVKCLi to BASE (θIG ← θBASE + θNK + ADVKCLi).

After setting the ignition timing θIG in step S304 or step S306, step S3
In step 07, the ignition timing ADV is set by converting the ignition timing θIG indicated by the crank angle into time. In this embodiment, since the timing of the ignition timer is started with the θ2 crank pulse as a trigger, the angle between the crank pulses between BTDC θ1 and θ2 and the crank pulse input interval time Tθ1
Then, the ignition timing θIG is divided by the cycle (angular velocity) ω12 calculated based on 2 to set the ignition time ADV (ADV ← θIG / ω12).

Then, at step S308, the ignition time AD
V is set in the ignition timer, and in step S309, θ2
Timing is started with the crank pulse as a trigger. When the ignition time ADV is reached, an ignition signal is output to the igniter 19 of the cylinder #i to be ignited in step S310, and the routine exits.

In the above-described correction of the ignition timing of each cylinder based on the differential rotation average value TCLAVEi, variations in the output torque between the cylinders can be suppressed, and unpleasant low-frequency vibrations can be prevented, and smooth idle rotation can be achieved. Thus, the driving feeling can be improved.

In contrast to the correction of the fuel injection amount, in the correction of the ignition timing, a slight correction of the ignition timing greatly changes the volumetric efficiency and has a greater correction effect. By using the fuel injection amount correction and the cylinder-specific ignition timing correction based on the differential rotation average value TCLAVEi in parallel to perform the correction in parallel, it is possible to finally reduce the difference between the fuel injection correction amounts of the cylinders. As a result, the combustion state of each cylinder can be made uniform, the idle stability can be improved, and harmful exhaust emissions can be reduced in total.

In the present embodiment, the differential rotation TC
The YLAC is calculated by subtracting the engine rotation speed TCYLi-1 corresponding to the cylinder # i-1 one combustion stroke earlier from the engine rotation speed TCYLi corresponding to the current combustion stroke cylinder #i. The engine rotation speed TCYLi corresponding to the current cylinder #i may be subtracted from the engine rotation speed TCYLi-1 corresponding to the cylinder # i-1 one combustion stroke earlier to obtain the differential rotation TCYLAC of the cylinder #i. In this case, the average output torque and the differential rotation average value TCLAVE
Is reversed, the ignition timing advance and retard corrections are reversed, and the ignition timing is advanced and corrected for the cylinder having the highest differential rotation average value TCLAVE to obtain the differential rotation average value TCLAV.
The ignition timing is retarded for the cylinder with the lowest E.

Further, in the present embodiment, the engine speed (engine speed) is used as the engine speed state quantity. However, the present invention is not limited to this. The rotational angular velocity or the engine rotational angular acceleration may be used.

[0104]

As described above, according to the first aspect of the present invention, the amount of engine rotation at each predetermined crank angle between cylinders is detected, and when the engine is idling, it corresponds to the current combustion stroke cylinder. Subtract the engine rotation state amount corresponding to the cylinder one combustion stroke before from the engine rotation state amount,
It is calculated as a differential rotation state amount for the current combustion stroke cylinder. Then, the average value of the differential rotation state amount for each cylinder is calculated by averaging the differential rotation state amount for each cylinder in the predetermined period, and the differential rotation state amount and the differential rotation state amount average value for each cylinder in the predetermined period. Is integrated to calculate an integrated value of the differential rotation fluctuation amount for each cylinder. Then, the fuel injection amount of the cylinder having the smallest differential rotation fluctuation amount is corrected to be reduced, and the fuel injection amount is corrected to be increased for the cylinder having the maximum difference rotation fluctuation amount. The ignition timing of the cylinder having the lowest average value of the differential rotation state amount is advanced, and the ignition timing of the cylinder having the highest average value of the differential rotation state amount is retarded. The output torque among the cylinders can be made uniform by suppressing the variation of the output torque, the unpleasant low-frequency vibration can be suppressed, the idling operation can be stabilized, and the harmful exhaust emission can be totally reduced. Fuel efficiency can be improved.

Further, as in the second aspect of the present invention, when the engine is in the idling state, the difference between the engine rotation state amount corresponding to the cylinder one combustion stroke before and the current combustion stroke state is determined as the differential rotation state amount with respect to the current combustion stroke cylinder. The calculation may be performed by subtracting the engine rotation state quantity corresponding to the cylinder.In this case, the ignition timing advance and retard corrections are reversed, and the ignition timing is calculated for the cylinder having the highest differential rotation state quantity average value. Is advanced, and the ignition timing is retarded for the cylinder having the lowest differential rotation state amount average value. According to the second aspect of the present invention, the same effect as that of the first aspect can be obtained.

According to the third aspect of the invention, when the fuel injection amount and the ignition timing are corrected in the idling state, the fuel injection for increasing or decreasing the fuel injection amount in accordance with the integrated value of the differential rotation fluctuation amount. The correction amount is set for each cylinder, and the final fuel injection amount is set for each cylinder by correcting the fuel injection amount calculated based on the engine operating state with the cylinder-specific fuel injection correction amount. Further, during the idle state, the ignition timing correction amount for advancing or retarding the ignition timing according to the average value of the differential rotation state amount is set for each cylinder, and the ignition timing calculated based on the engine operation state is set for each cylinder. The final ignition timing is set for each cylinder by correcting with the timing correction amount. Since the cylinder-by-cylinder fuel injection correction amount and the cylinder-by-cylinder ignition timing correction amount are stored and held as learning values and updated as needed, the controllability can be further improved in addition to the effect of the first aspect of the present invention. It has the effect of being able to.

[Brief description of the drawings]

FIG. 1 is a flowchart of an idle stabilization control routine (part 1);

FIG. 2 is a flowchart of an idle stabilization control routine (part 2);

FIG. 3 is a flowchart of an idle stabilization control routine (part 3);

FIG. 4 is a flowchart of an idle stabilization control routine (part 4);

FIG. 5 is a flowchart of a cylinder discrimination / engine rotation speed calculation routine.

FIG. 6 is a flowchart of a fuel injection control routine for each cylinder.

FIG. 7 is a flowchart of an ignition timing control routine for each cylinder.

FIG. 8 is a time chart showing a relationship among a crank pulse, a cylinder discrimination pulse, a combustion stroke cylinder, an ignition timing, and a fuel injection timing.

FIG. 9 is a timing chart showing a calculation state of a differential rotation for each cylinder.

FIG. 10 is an explanatory diagram showing a fluctuation state of a differential rotation.

FIG. 11 is an overall schematic diagram of an engine.

FIG. 12 is a front view of a crank rotor and a crank angle sensor.

FIG. 13 is a front view of a cam rotor and a cylinder discrimination sensor.

FIG. 14 is a circuit configuration diagram of an electronic control system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Engine 32 ... Crank angle sensor 35 ... Cylinder discrimination sensor 40 ... ECU (rotation state amount detection means, cylinder discrimination means, idling judgment means, difference rotation state quantity calculation means, difference rotation state quantity average value calculation means, difference rotation fluctuation NE: engine rotational speed (engine rotational state amount) TCYLAC: differential rotation (differential rotational state amount) TCLAVE: differential rotational average value (differential rotational state amount average value) TCLSUM: integrated value of differential rotation fluctuation amount INJKCLi: fuel injection correction amount Ti: fuel injection pulse width (fuel injection amount) ADVKCLi: ignition timing correction amount θIG: ignition timing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI theme coat ゛ (Reference) F02P 5/15 F02P 5/15 B F-term (Reference) 3G022 AA03 CA03 DA01 DA02 EA07 EA10 FA04 FA05 GA01 GA05 3G084 AA03 BA13 BA17 CA03 DA02 DA10 DA11 DA23 DA39 EA05 EA07 EB12 EB20 EB25 EC04 FA00 FA33 FA34 FA38 FA39 3G301 HA06 JA02 JA05 JA21 KA07 LA00 MA11 NA01 NB03 ND02 ND25 PE00Z PE02Z PE03Z PE04Z PE05Z

Claims (3)

[Claims] 1. An engine rotation state amount detection means for detecting an engine rotation state amount for each predetermined crank angle between cylinders; a cylinder determination means for determining a current combustion stroke cylinder; And when the engine is idle, subtracts the engine rotation state quantity corresponding to the cylinder one combustion stroke earlier from the engine rotation state quantity corresponding to the current combustion stroke cylinder, and calculates the current combustion stroke cylinder. A differential rotation state quantity calculating means for calculating the differential rotation state quantity with respect to a cylinder; and a differential rotation state quantity for averaging the differential rotation state quantity for each cylinder in a predetermined period and calculating an average value of the differential rotation state quantity for each cylinder. An average value calculating means for integrating an absolute value of a difference between the differential rotation state amount and the average value of the differential rotation state amount for each cylinder in a predetermined period; A differential rotation fluctuation integrated value calculating means for calculating as a differential rotation fluctuation integrated value; and a fuel injection amount reduction correction for the cylinder having the smallest differential rotation fluctuation integrated value in an idling state; A fuel injection control means for increasing and correcting the fuel injection amount for the cylinder having the largest integrated value; and advancing the ignition timing for the cylinder having the lowest differential rotation state amount average value, An engine control device comprising: ignition timing control means for retarding the ignition timing of a cylinder having the highest value. 2. An engine rotation state quantity detection means for detecting an engine rotation state quantity for each predetermined crank angle between cylinders; a cylinder determination means for determining a current combustion stroke cylinder; And when the engine is in an idle state, subtracts the engine rotation state amount corresponding to the current combustion stroke cylinder from the engine rotation state amount corresponding to the cylinder one combustion stroke before, and calculates the current combustion stroke cylinder. A differential rotation state quantity calculating means for calculating a differential rotation state quantity for the cylinder, an average processing of the differential rotation state quantity for each cylinder in a predetermined period, and calculating a differential rotation state quantity average for each cylinder. Value calculating means for integrating the absolute value of the difference between the differential rotation state amount and the differential rotation state amount average value for each cylinder in a predetermined period, A differential rotation fluctuation integrated value calculating means for calculating as the rotation fluctuation integrated value; and, during idling, the fuel injection amount is reduced and corrected for the cylinder having the smallest differential rotation fluctuation integrated value. A fuel injection control means for increasing and correcting the fuel injection amount for the cylinder having the largest value; an advance correction of the ignition timing for the cylinder having the highest differential rotation state amount average value; and a differential rotation state amount average value. An ignition timing control means for retarding the ignition timing of a cylinder having the lowest ignition timing. 3. The fuel injection control means sets, for each cylinder, a fuel injection correction amount for increasing or decreasing the fuel injection amount in accordance with the differential rotation fluctuation amount integrated value in an idle state. The fuel injection amount calculated based on the above is corrected by the above-described cylinder-by-cylinder fuel injection correction amount to set a final fuel injection amount for each cylinder, and the above-mentioned cylinder-by-cylinder fuel injection correction amount is stored and held as a learning value and updated as needed. In the idle state, the ignition timing control means sets an ignition timing correction amount for advancing or retarding the ignition timing according to the average value of the differential rotation state amount for each cylinder, and based on the engine operating state. The calculated ignition timing is corrected by the cylinder-specific ignition timing correction amount to set the final ignition timing for each cylinder, and the cylinder-specific ignition timing correction amount is stored and held as a learning value and updated as needed. The engine control device according to claim 1 or 2, wherein